I'm all for any relationship style that makes the consenting adults in them happy, but having engaged in group relationships repeatedly, I also feel that I should point out that the more people you have in the primary relationship, the more it can exponentially increase the amount of conflict that can arise. Not that it can't be mitigated, if everyone is mature, communicates clearly and is good at tackling molehills before they become mountains.
Most people never even give a thought to the fact that a lot of couples find it challenging to adjust to go from a life where what they want is all that matters, to a life where they have to consider another person in pretty much everything they do. Having to consider two separate people really adds another dimension to that adjustment. (And, of course, you have to find those two, first!)
But if you can make it work, congratulations and more power to you!
